Hi all, I have some Zu Audio Soul Superflys that I am setting up in a listening area for the bedroom and was wondering if the SuperZen would be a good match?

The speakers are 16 ohm at 101dB and I read a review (Tone Audio #35 - Feb, 2011) that a MiniWatt N3 was a good match, so I was thinking a Decware would be even better (not to mention I like to spend my dollars in America when possible).

However the SuperZen does not have as many watts as the MinWatt N3, so I also thought that the Zen Triode Integrated might be a better match, but it's just that the price of the SuperZen is well within my budget in comparison with the Zen Triode Integrated.

Call Steve and discuss with him. Decware used to offer a choice of output trannys, the standard, good for low impedance loads, and the "EX" version, geared for higher impedance speakers like yours. If your zen has the inappropriate one, you won't get full power to the speakers.

You can select output transformers from the shopping cart when you price a SuperZen.

a) for speakers between 2 and 6 ohmsb) for speakers between 6 and 16 ohms.

It does not change the price.

While it's true running an 8 or 12 ohm speaker with option a) will put less power to the speakers, that is in fact what I sent Tone Audio. The reason the comments were still positive is because the speakers were efficient enough that the reduced power was insignificant.

Obviously SOME speakers are going to fall in the middle and work with either a) or b). That is because a speakers impedance is really a varying load across it's frequency response.

Here is a typical 8 ohm speaker's impedance plot:

You can see around 50 Hz and between 100 & 500Hz the speaker is actually closer to 4 ohms.

Option a) would put out more power as the impedance drops, meaning a nice solid hitting bass and mid bass.

Option b) would put out less power as the impedance drops, making for a leaner sounding bass and mid bass. Low bass below 40 Hz would be slightly improved if the speaker has any real output there.

Of course every loudspeaker's impedance plot is different. And it's only important to know what it is if you plan to run 6 ~ 8 ohm speakers as they fall in the zone where either transformer might sound best.

As a general observation I can tell you that if you have high efficiency single driver speakers that are rated at 8 ohms, option b) is almost always the best, giving the speaker more weight and midrange tone.

Here is a plot of a popular 8 inch fostex driver to support this statement.

Very helpful post, Steve. Could you tell us the optimum impedance for best power transfer for each case, i.e. for the Super Zen, standard output tranny, in stereo, x ohms(?); bridged Super Zen, standard output tranny, x ohms (?); etc. That would be good info to include on the "which amp to choose" page.

Busterfree, do you happen to have an impedance graph for your speakers? If you do, you can use that info, combined what Steve posted, to determine the best match for you. A bridged zen will see half the impedance across the board but the shape of the curve doesn't change. For example, take the first impedance graph that Steve posted of a typical 8 ohm speaker and halve the y-axis impedance scale; now the low areas at 50 hz and from 100-500 hz (the frequencies demanding the bulk of the power) are more like 2 ohms, thus would probably be an excellent pairing with bridged zens. That would provide very good power transfer throughout the primary power band, and give a nice, warm, full presentation. Or so one would reasonably guess, looking just at these few specifics.

Along with Busterfree, I too am still curious as to how bridging affects output impedance. The fact that I distinctly prefer a single zen with my own big box, "8 ohm nominal" impedance, high sensitivity speakers tells me that in spite of the reasoned approach to impedance matching and power delivery, that something else is going on. Specifically, if the output impedance jumps as a result of bridging (not sure if this is the case or not, please correct me), it would be even more reactive into a speaker load. Those of us using big box, three way, high sensitivity speakers (those not specifically designed to be an easy, flat-ish impedance load for SET amps) may be looking this speaker/amp matching issue right in the face.

Unfortunately, I have not found an impedance curve for my speakers yet, but the search continues. I have Klipsch Forte II, Klipsch RB81, and Trapezium speakers. The Forte II are in the closet, and I am using the SE34I.3 with the RB81. I have a small listening space at the moment.

I am just curious more than anything else. The SE84C+ sounded great with the Forte II a while back. I will only have one super zen, and I plan to keep using it with the Trapeziums.

My main speakers are Tekton 8.1en's which are based on the Fostex 206en rated 96dB 1m/1w @ 8ohms. I'm thinking of ordering the SE84CKC which needs a pre-set impedance decision. According to Steve, selection "b" would be the one.

What happens if you run speakers rated at 4 ohms? I currently use the Tektons with my DIYSE84 with plenty of volume with the pot set ~40%. I don't have any speakers rate at 4 ohms, but any speakers available at Decware seem to be around 4 ohms.Regards,Hank

Hey, buster, that's what I have too. With the fortes, the impedance is in the 4 ohm range over the woofer's band below 600hz with a couple peaks down low. The impedance in the midrange (600-6000) is sky high because of the autoformer (and in spite of that, the mid's ridiculous sensitivity still causes it to play a tad hot relative to the woof and tweet when driven with a zen). Corners are your forte's friend to restore the bass, and PWK designed them that way to begin with, so don't be afraid to try it. I prefer the stepped-down tweets and would equalize for that if the amp didn't do it inherently. Forte II w/ a zen is friggin' sick when you get the placement right, and for a small room that's corner loaded, cross-fired slightly in front of the listening position. Get those fuckers out of the damn closet already and hook 'em up!

Buster, I once had the Forte I's with a Select....nice!! I only wish I still had the select when I upgraded the Forte's with Bob Crites' crossovers and diaphragms. If you're keeping your Forte, I'll bet mucho money that the Crites upgrades and the CKC will be the business!! Fresh Sonicaps capacitors go a long way in discharging the signal quicker (less absorption of the signal). Doesn't change the impedance because all values of the caps, resistors, and transformer are the same...just better quality and fresher (not 35 plus years old)

Thanks guys...The Forte II are great. Keeping them in the closet keeps me out of trouble with my neighbors. I am in an apartment. I am the original owner, and I had someone redo the crossovers about 10 yrs ago. I will be upgrading the tweeters and crossover again when I put them back in place. These are a set of speakers that I will never sell...

Ordering my SuperZen right after the New Year ... I guess were both in for a treat!

Not to knock this off topic, but did you see Zu has a new version of the Souls coming out? They are called the Soul Supreme and are topped out nicely. They still have the same super efficient cross-over-less design (i.e. 16ohm and 101dB), but now also share a lot of the same components as their top of the line Dominance and Definition MK IVs - like the Zu103ND/G1-16 full-range driver, the Radian 850 based tweeter and the ZuB3 connector posts.

So many cool things to buy ... too little $$$ ... that's all I'm going to say about that

I've heard a little about them, not much on their website about them yet. I will probably give the new nanotech drivers a try sometime this winter. That will be 2 nice upgrades! Only thing that's been holding me back on the Decware amps is no remote control, as I find myself changing the volume often while listening & reading on my ipad. Recently sold my Cayin A55 integrated with remote, it was very nice. But now I'm ready to see what all the Decware fuss is about! I luv the anticipation of waiting on a new piece of gear!